Kit of parts for use in retracting body tissue

ABSTRACT

A retractor for use in spinal surgery comprises a frame including a ring member defining a generally central interior space. A plurality of blades is releasably supported respectively to slidable arms each supported on the ring member for individual translational movement relative to the ring member. The blades define an initial substantially enclosed opening that is expandable for use in a surgical procedure. A clutch mechanism supported on the ring member is associated with each arm to individually selectively engage each such arm with a rotatable main gear such that upon rotation of the main gear by a single actuator any one, all or any desired combination of arms may be translated relative to the ring member to move the blades and expand the opening in one or more selected desired directions.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.13/891,697, filed May 10, 2013, now U.S. Pat. No. 8,727,975, the entirecontents of which are incorporated by reference herein.

FIELD OF THE INVENTION

The subject invention relates generally to the field of retractors forretracting bodily tissue during surgery and more particularly to aretractor for use in spinal surgery.

BACKGROUND OF THE INVENTION

Retractors are commonly used in surgical procedures to separate andexpand an incision to access the surgical site and to minimize trauma tothe patient. While there are many styles, shapes and sizes ofretractors, the typical retractor used in spinal surgery comprises aplurality of retractable blades, which may include two to four or moreblades that are introduced through the surgical incision to form aprotected corridor to the surgical site. Various mechanisms are providedto move one or more blades in different directions so as to expand theincision and to hold the blades in the expanded position. One factor inthe surgeon's decision as to the type of retractor used is the controlof the blade movement. Blades are often configured to not only expandoutwardly so as to expand the corridor but also to pivot or toe at theirdistal ends so as to increase the opening of the corridor adjacent thesurgical site. In addition, the size of the retractor is often ofconsequence, with the surgeon typically seeking to minimize the overallfootprint of the retractor for ease of handling, placement and useduring surgery.

Accordingly, it is desirable to provide a retractor that not onlysatisfies these needs but also provides additional flexibility in theuse, adjustability and control of the movement of the blades duringspinal surgery.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an improved retractor foruse during surgery, particularly spinal surgery.

DESCRIPTION OF THE FIGURES

FIG. 1 is a top perspective of a retractor in accordance with anembodiment of the present invention for use during spinal surgery.

FIG. 2 is a partially exploded top perspective view of the retractor ofFIG. 1.

FIG. 3 is a top plan view of the retractor of FIG. 1 with the covers andthe mounting bracket removed for clarity.

FIG. 4 is a top perspective view of one translatable arm of theretractor of FIG. 1 with a retractor member including a blade attachedthereto with a switch being oriented in a first position.

FIG. 5 is a partial top perspective rear view of the retractor membershown in FIG. 4.

FIG. 6 is a longitudinal cross-sectional view of the arm and retractormember of FIG. 4.

FIG. 7 is a side elevation view of the arm shown in FIG. 4 with theblade in a toed position.

FIG. 8 is a top perspective view of the translatable arm and retractormember of FIG. 4 with the switch being oriented in a second position.

FIG. 9 is a partial side view of the retractor of FIG. 3 as viewed alongthe direction line IX in FIG. 3 with a portion of the retractor frameremoved to reveal only the gearing mechanism in one quadrant of theretractor with the switch in the first position of FIG. 4.

FIG. 10 is a further partial side view of the retractor gearingmechanism shown in FIG. 9 with the switch in the second position of FIG.8

FIG. 11 is a further top plan view of the retractor shown in FIG. 3 withall the translatable arms and blades supported thereon having beentranslated radially outwardly to expand the surgical corridor.

FIG. 12 is a further top plan view of the retractor shown in FIG. 3 withone of the translatable arms and blade supported thereon having beentranslated radially outwardly to expand the surgical corridor in aselected direction.

FIG. 13 is a top perspective view of an alternative translatable armwith a retractor member supported thereon and a switch oriented in afirst position.

FIG. 14 is a cross-sectional view of the alternative arm arrangement ofFIG. 13.

FIG. 15 is a top perspective view of the alternative arm arrangement ofFIG. 13, with the switch oriented in a second position.

FIG. 16 is a partial side view of the retractor of FIG. 3 as viewedalong the direction line IX in FIG. 3 with a portion of the retractorframe removed to reveal only the gearing mechanism in one quadrant usedwith the alternative arm arrangement of FIG. 13 with the switch in thefirst position of FIG. 13.

FIG. 17 is a further partial side view of the retractor gearingmechanism shown in FIG. 16 with the switch in the second position ofFIG. 15.

DESCRIPTION OF THE EMBODIMENTS

For the purposes of promoting and understanding the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and described in the following written specification. It isunderstood that no limitation to the scope of the invention is therebyintended. It is further understood that the present invention includesany alterations and modifications to the illustrated embodiments andincludes further applications of the principles of the invention aswould normally occur to one skilled in the art to which this inventionpertains.

Referring to FIG. 1, a retractor 10 is shown in a particular arrangementfor use in spinal surgery. In the arrangement shown, retractor 10comprises four blades 12 each being identical and spaced radiallysubstantially equally at approximately 90° relative to each other. Theblades 12 project substantially transversely downwardly from a frame 14toward a human spine 16 to define an expandable minimally invasivecorridor through which a surgical procedure including the implantationof an implant into an intradiscal space 18 of the spine 16 may beperformed. As will be described, the blades 12 are supported by theretractor 10 whereby one or all or any combination of blades 12 may betranslated in a radial direction from a single source actuator to expandan incision through bodily tissue in a controlled manner.

In the spinal surgical procedure illustrated in FIG. 1 the use of theretractor 10 is from a direct lateral approach to the surgical site. Theretractor 10 is oriented to define four quadrants A, B, C and D, withquadrant A being in the caudal direction, quadrant B being in theanterior direction, quadrant C being in the cephalad direction andquadrant D being in the posterior direction. The desired orientation maybe maintained as will be further described by a bracket 20 suitablyattached to the frame 14 of retractor 10 with the bracket 20 suitablyconnected to a rigid mounting arm connected to an operating table onwhich the patient is lying.

Turning now to FIGS. 2-3, further details of the retractor 10 aredescribed. Frame 14 comprises a lower ring member 22 defining agenerally central fully enclosed interior space 24. Frame 14 includes acover 26 of substantially the same structure associated with each of thequadrants A, B, C and D each of which covers a gear mechanism for use inselectively translating the blades 12, as will be described. The ringmember 22 supports four arms 28 one each at the quadrants A, B, C and D,each arm 28 supporting a blade 12 at a distal portion 28 a thereof. Thearms 28 are each radially individually translatable on the ring member22 with the distal portions 28 a and blades attached thereto beingmovable within the interior space 24 along the radial directionsindicated by arrows 30 in FIG. 3.

Still referring to FIGS. 2-3, ring member 22 supports a transmissionmember defined by a main gear 32 for rotational movement relative toring member 22 and thereby relative to each arm 28. Main gear 32comprises a plurality of gear teeth 32 a extending around thecircumference of main gear 32. Ring member 22 supports an actuator 34disposed in this particular arrangement between quadrants A and D. Thelower portion of actuator 34 defines a drive gear 34 a having gear teeth34 b (see FIG. 9) in engagement with teeth 32 a on the main gear 32. Theupper portion of actuator 34 defines a hex portion 34 c configured forengagement with a suitable tool such as, for example, a tool with aT-handle (not shown) having a complementary hex portion. Rotation of thetool rotates actuator 34 and the drive gear 34 a which in turn rotatesmain gear 32. Associated with each arm 28 and supported by ring member22 in each of the quadrants A, B, C and D is a clutch mechanism 36 thatis configured to selectively engage a selected arm 28 with the main gear32, as will be detailed hereinbelow. Also associated with each arm 28and supported by ring member 22 in each of the quadrants A, B, C and Dis a locking mechanism 38 that cooperates with each arm 28 to allowtranslational movement of such arm 28 in only one direction and lockingin the opposite direction, as will be described in further detail.Between each of the quadrants A, B, C and D ring member 22 is configuredto have a mounting portion 40 by which the retractor 10 may be directlyconnected to the operating table by a mounting arm or to which bracket20 may be connected for attachment to the mounting arm.

Referring now to FIGS. 4-7 further details of the blades 12, theattachment to the arms 28 and a pivoting or toeing motion of the blades12 are described. A retractor member 41 for releasable attachment toeach housing 28 comprises blade 12 and a blade support 43. Blade support43 is disposed at the proximal end 41 a of retractor member 41. Eachblade 12 is elongate and includes a proximal end 12 a attached to bladesupport 43 and a distal end 12 b. An outer surface 12 c extending alongthe length of the blade 12 is configured to have a concave surface toform a quadrant of a surgical corridor formed by the four blades 12having a substantially enclosed opening 42 as shown in FIG. 1. Asillustrated in FIG. 5, blade support 43 includes a dovetail slot 43 athat cooperates with a complementary dovetail slot 28 b in distalportion 28 a of arm 28 for releasably mounting retractor member 41thereto. The blade support 43 includes a flange 43 b which serves as astop to properly seat retractor member 41 as the dovetail slots engageduring insertion of retractor member 41 from above distal portion 28 a.Blade support 43 may include an opening 43 c extending obliquely throughan upper surface 43 d and opening through concave surface 12 c. Opening43 c may be used for insertion of a light cable or other optical deviceto illuminate the opening 42 of the surgical corridor. The retractormember 41 with blade 12 is releasably secured by a set screw 44threadedly received in a threaded opening 28 c. The bottom of said screw44 is received in a recess 43 e formed in a side face 43 f of the bladesupport 43.

With further reference to FIGS. 6-7, each arm 28 comprises a housing 46to which the distal portion 28 a is pivotally attached by a pivot pin48. The distal portion 28 a includes a threaded opening 28 d forthreadedly receiving therein a toeing screw 50 the upper portion 50 a ofwhich is threaded to engage the threads of threaded opening 28 d. Thelower portion is formed to have a generally spherical portion 50 b thatis movably situated in a housing cavity 46 a. As toeing screw 50 isthreaded into threaded opening 28 d generally spherical portion 58 bwill contact surface 46 b of the housing 46 causing the distal portion28 a of the arm 28 to pivot about pivot pin 48 as shown in FIG. 7.During the pivoting motion the generally spherical portion 50 b willmove within cavity 46 a along surface 46 b as the toeing motioncontinues. Retractor member 41 with blade 12 that is attached to distalportion 28 a likewise pivots with the pivoting of distal portion 28 a.Toeing movement up to about 30° may be achieved to further expand theopening 42 at the distal ends 12 b of the blades adjacent the surgicalsite.

Referring still to FIGS. 4 and 6 and with additional reference to FIGS.8-10, elements of the clutch mechanism 36 are described. The housing 46of each arm 28 movably supports therein an elongate bar such as anelongate shaft 52. Shaft 52 in this particular arrangement is generallycircular and is supported for rotation about its longitudinal axis 52 awithin housing 46. A series of linearly arranged gear teeth 54 isprovided lengthwise along the periphery of shaft 52 at least over aradial portion 52 b of the shaft 52 as depicted in FIG. 4. Anotherseries of gear teeth 55 (See FIGS. 9 and 10) is arranged arcuatelyaround a portion of the periphery of shaft 52, the function of whichwill be described hereinbelow. The radial portion 52 c of the shaft 52without gear teeth 54 along its length is illustrated in FIG. 8. In thisparticular arrangement, the teeth 54 extend over a radial portion 52 bof about 90°, it being understood that the radial extent having teeth 54may vary, provided there is both a longitudinal extent with teeth 54 anda longitudinal extent without teeth. Still referring to FIGS. 4 and 6, aswitch 56 is rotatably supported by housing 46. Switch 56 comprises arotatable knob 58 that is attached to a switch gear 60 for jointrotation therewith. Switch gear 60 includes a plurality of gear teeth 60a that are in engagement with teeth 55 on shaft 52. Thus, in a firstposition as shown in FIGS. 4 and 9, teeth 54 are arranged to be exposedthrough a window 46 c of housing 46 with knob 58 in a first orientationand gear teeth 60 a are in engagement with gear teeth 55 on shaft 52.Rotation of the knob 58 approximately 180° to the orientation shown inFIGS. 8 and 10 rotates the switch gear 60 which in turn throughengagement of teeth 60 a with teeth 55 rotates shaft 52 about axis 52 aapproximately 90° to a second position until the portion 52 c of theshaft 52 without gears is exposed through window 46 c. Through suchrotation of shaft 52 the arm 28 may be selectively engaged with the maingear 32 as part of the clutch mechanism 36. As will be described, theteeth 54 on the shaft 52 effectively function as a rack to convert therotary motion of the main gear 32 into linear motion for translating thearm 28 relative to the ring member 22 through the clutch mechanism 36.

Referring again to FIG. 3 and also to FIG. 9, further details of theclutch mechanism 36 are described. In the particular arrangement beingdescribed, clutch mechanism 36 includes a coupling gear mechanism 62comprising three step gears 64, 66 and 68 all of which are in engagementwith each other. The step gears 64, 66 and 68 are used in the couplinggear mechanism 62 so as to provide a desired gear reduction between therate at which main gear 32 rotates and the rate at which each arm 28translates relative to ring member 22. As such, coupling gear mechanism62 may allow an arm 28 to translate at 1 mm increments for each onequarter turn of actuator 34. Step gear 64 comprises an upper smallergear 64 a and a lower larger gear 64 b. Larger gear 64 b has gear teethin engagement with the gear teeth 32 a of main gear 32 and as such whenmain gear 32 rotates it will rotate larger gear 64 b. Step gear 66comprises an upper larger gear 66 a and a lower smaller gear 66 b.Larger gear 66 a has gear teeth in engagement with gear teeth on smallergear 64 a of step gear 64. Step gear 68 comprises an upper smaller gear68 a and a lower larger gear 68 b. Larger gear 68 b has gear teeth inengagement with gear teeth on smaller gear 66 b of step gear 66.Rotation of the actuator 34 will effectively rotate the main gear 32 bythe drive gear 34 a with each of the step gears 64, 66 and 68 beingrotated as a result of engagement of step gear 64 with the main gear 32.Smaller gear 68 a of step gear 68 is positioned on ring member 22adjacent arm 28 so that the gear teeth thereon will be engageable withthe teeth 54 on shaft 52 which are exposed through window 46 c ofhousing 46.

As illustrated in FIG. 9, shaft 52 is in the first position describedwith respect to FIG. 4 wherein gear teeth 54 on shaft 52 engage theteeth of smaller gear 68 a. Teeth 55 are disposed on shaft 52 such thatthey do not make engagement with either the coupling gear mechanism 62or the locking gear mechanism. When switch 56 has been actuated to placeshaft 52 in such first position rotation of smaller gear 68 a willlinearly move shaft 52 through engagement with teeth 54 therebytranslating arm 28 radially with respect to ring member 22. Smaller gear68 a will effectively serve as the pinion to convert rotary motion ofthe coupling gear mechanism 62 into linear motion by engagement withteeth 54 on shaft 52 which, as described hereinabove, serves as a rack.It should be understood, however, that while coupling gear mechanism 62comprises three step gears 64, 66 and 68 in the particular arrangementbeing described, other gear mechanisms or a single coupling member maybe used in the retractor 10. For example, a single coupling member maybe defined by a single coupling gear with gear teeth with such singlegear being disposed on ring member 22 and such that the gear teeththereon are in engagement with gear teeth 32 a on main gear 32 and areengageable with teeth 54 on shaft 52.

Referring still to FIG. 3 and again to FIG. 10, details of the lockingmechanism 38 are described. In FIG. 10, shaft 52 has been rotated byswitch 56 to the second position as illustrated in FIG. 8. Duringrotation of switch 56, switch gear 60 has likewise been rotated causinggear teeth 60 a thereon through engagement with teeth 55 to have rotatedshaft 52 about its axis 52 a to the second position. In this secondposition, the radial portion 52 c of the shaft 52 without teeth 54 isexposed through window 46 c. As such, any rotation of smaller gear 68 athrough rotation of main gear 32 will not cause any translation of arm28. In this position, teeth 54 on shaft 52 are exposed through a window46 d formed through the housing 46 opposite window 46 c with the teeth54 being engageable with the locking mechanism 38. Locking mechanism 38comprises a locking gear 70 and an override gear 72. Locking gear 70 isa step gear that comprises an upper smaller gear 70 a and a lower largergear 70 b. Smaller gear 70 a has teeth engageable with teeth 54 on shaft52 when shaft 52 is in the second position, as illustrated in FIG. 10.Override gear 72 comprises a gear 72 a having gear teeth in engagementwith the gear teeth on larger gear 70 b. A pawl 74 is supported on ringmember 22 adjacent locking gear 70, the pawl 74 being spring-loaded by aspring element such as a torsion spring 76. Teeth 70 c on larger gear 70b are formed as ratchet teeth such that when teeth 70 c are inengagement with pawl 74 locking gear 70 can only rotate in one directionis indicated by arrow 78 in FIG. 3. As such, in the second position ofshaft 52 as shown in FIG. 10, wherein teeth 54 are in engagement withthe gear teeth of smaller gear 70 a, arm 28 is prevented fromtranslating radially inwardly relative to ring member 22. Release of thepawl 76 from the gear teeth 70 c on larger gear 70 b will allow freerotation of locking gear 70 whereby arm 28 may be freely and manuallytranslatable.

With pawl 76 still in engagement with gear teeth 70 c on larger gear 70b arm 28, while being prevented from translating radially inwardly, maybe independently translated radially outwardly upon rotation of overridegear 72. Override gear 72 comprises an upper portion 72 b having anengagement surface such as a hex configuration for engagement with acomplementary surface on a suitable instrument (not shown) for rotatingoverride gear 72. Rotation of override gear 72 causes gear 72 a torotate locking gear 70 through engagement with larger gear 70 b. Withthe gear teeth on smaller gear 70 a being in engagement with teeth 54 onshaft 52, shaft 52 translates radially outwardly upon rotation ofsmaller gear 70 a. Pawl 76 will prevent translation of shaft 52 radiallyinwardly. While the teeth 54 on shaft 52 are shown in FIGS. 10 and 11 asextending over a radial extent to engage gear mechanism 62 in the firstposition and the locking mechanism 38 in the second position, teeth 54may be configured on shaft 52 to extend over a radial extent to engageboth the coupling gear mechanism 62 and the locking mechanism 38 whenthe shaft 52 is being rotated from the first position to the secondposition. Such a construction would substantially prevent arm 28 fromradially slipping during the transition between the first to the secondposition.

Having described the details of the retractor 10, further aspects of theconstruction of the retractor 10 are described. For example, in thearrangement for use in spinal surgery particularly from the lateralapproach, the retractor frame 14 may have a maximum outer diameter ofabout 5.26 inches. As such, the retractor 10 will be relatively easy tohandle by a surgeon, will present a relatively small footprint andgenerally fit between a patient's iliac crest and ribs during surgery.For this application, all the components of the retractor 10 may beformed of aluminum except for the gears which would be formed ofstainless steel. The aluminum components are desirable for not onlytheir strength and rigidity but also for use with fluoroscopic imagingwhereby the aluminum material is not fully opaque but allows a degree oftranslucency to aid fluoroscopic visibility for the surgeon.

During use of the retractor 10 in this particular arrangement, a surgeonforms an initial incision through the tissue of the patient from thelateral aspect in a manner to create a surgical corridor through thepsoas muscle down to a surgical site adjacent the lateral surface of aspinal disc. The initial incision may be dilated by a series ofsequentially larger dilation cannulas as is conventionally known in theart to further expand the incision. Detection of nerves during thedilation process may be performed as is known in the art by conventionalneural monitoring techniques. Suitable dilation and neural monitoringtechniques are described, for example, in commonly assigned PCTApplication Number PCT/US12/54051, entitled “Apparatus for DilatingBodily Tissue and for Monitoring Neural Activity in the Dilated BodilyTissue”, filed Sep. 7, 2012, and published as WO 2013/036705A1 on Mar.14, 2013, this PCT Application being incorporated herein by reference inits entirety.

After suitable dilation and nerve detection, the surgeon will determinethe depth of the corridor and the length of blades 12 to be used inretractor 10. A kit may be provided with a set of different lengthblades 12, together with various other instruments and tools for useduring surgery. The length of blades 12 may range from 9 cm-17 cm. Oncethe proper length is determined, the surgeon will select a set of fourretractor members 41 having blades 12 of any desired length and attachone retractor member 41 to each arm 28 of the retractor 10 as describedhereinabove. The retractor members 41 on arms 28 will be adjusted to aninitial position as depicted in FIG. 3 wherein the distal ends of theblades 12 form the substantially enclosed opening 42. As used herein, asubstantially enclosed opening means an opening wherein the longitudinaledges of each of the blades 12 are in contact or a substantially smallspace exists between each of the blades 12 along their lengths. Theopening 42 is formed so that the blades 12 simultaneously slide over thelargest of the sequential dilation cannulas in a relatively closesliding fit. In some instances the blades 12 may be formed to have anarcuate extent less than the arcuate extent of the blades supports 43,as seen in FIG. 4. As such, the side edges of the blade supports 43 maybe in contact as the retractor 10 is positioned over the largestdilation cannula with a small gap between the longitudinal edges of theblades along the lengths. For this particular application, the initialopening 42 may range from 13 mm-18 mm, although different openingconfigurations and positions may be achieved.

After the blades 12 are inserted into the incision over the largestdilation cannula, the retractor 10 is rigidly secured to the operatingtable by bracket 20. Bracket 20 as shown in FIGS. 1-2 is generallyhorse-shoe shaped with a pair of arms 20 a and 20 b each terminatingwith a thumbscrew 80 and 82. Thumbscrew 80 terminates in a threadedportion 80 a for threaded engagement in a threaded hole 40 a in onemounting portion 40 and thumbscrew 82 terminates in a threaded portion82 a for threaded engagement in threaded hole 40 a in a second mountingportion 40. The distal ends of each mounting bracket arm 20 a and 20 bmay be configured to have a polygonal shape to match a complementarypolygonal shape in each mounting portion 40 so as to provide a secure,rigid connection between the retractor frame 14 and the bracket 20.Bracket 20 includes a mounting portion 20 c at the base of the bracket20 formed similarly to mounting portions 40 for secure connectionthereto to a rigid mounting arm which in turn is connected to theoperating table. While it should be appreciated that an individualmounting portion 40 on the retractor frame 14 may be used to attach theretractor 10 to the operating table via a rigid mounting arm, use of thebracket 20 which attaches to at least two mounting portions 40 on theretractor 10 provides a more stable, rigid connection.

With the retractor 10 rigidly connected to the operating table in amanner to maintain the position of the retractor stable during thesurgical procedure, the dilation cannulas may be removed from theincision. The surgeon may now select which quadrants of the opening 42may be expanded. For example, if the surgeon wishes to expand theincision in all of the quadrants A, B, C and D, switch 56 on all of thehousings 46 would be rotated to the first position as depicted in FIG.4. With a suitable tool the surgeon will rotate actuator 34 which willrotate main gear 32 and through the clutch mechanism 36 all arms 28 willtranslate radially outwardly upon rotation of the actuator 34, expandingthe initial opening 42 equally in all directions to the expanded opening42 a as shown in FIG. 11. The initial opening 42 may be increased to anexpanded opening 42 a in the range of 14 mm-36 mm, although othersuitable ranges are contemplated based upon the application. Smallerexpansion may be desirable wherein an implant is inserted through theexpanded opening to the surgical site, such as in the intradiscal space,while a larger expansion may be desired when additional surgicalprocedures, such as subsequent grafting around the implant are performedthrough the retractor. Any or all of the distal ends 12 b may be furtherexpanded radially outwardly in a toeing manner as described hereinabovewith respect to FIG. 7. Suitable illuminating elements may be used inconjunction with one or more retractor members 41 as describedhereinabove either before or after blades 12 are radially expanded ortoed.

In certain situations, the surgeon may wish to radially expand thedilated incision in only one direction, such as in quadrant A. In thisprocedure, the surgeon would position switch 56 on arm 28 in quadrant Ain the first position while moving switch 56 on the remaining arms 28 inquadrants B, C and D to the second position. Rotation of the actuator bythe suitable tool rotates main gear 32 and with only arm 28 in quadrantA being selectively engaged with main gear 32 through its associatedclutch mechanism 36, only this arm 28 will translate radially outwardlyas shown in FIG. 12. As such, a surgeon may selectively translate anyone or all of the arms 28 or any combination of arms 28 in the use ofretractor 10 in one or more selected desired directions from a singlesource, such as actuator 34.

Having described a particular arrangement of retractor 10, it should beunderstood that variations may be made thereto within the contemplatedscope of the invention. For example, as an alternative to movable barbeing a rotatable shaft 52, the movable bar may be provided toselectively move linearly between the first position and a secondposition described hereinabove. As illustrated in FIGS. 13-17, a bar 152supported in a modified arm 128 having a housing 146 is movable in atransverse direction from the first position to the second position, aswill be described. Bar 152 is elongate and generally rectangulardefining a longitudinal axis 152 a. Gear teeth 154 b are linearlydisposed on one lateral side of bar 152 that faces smaller gear 68 a ofthe coupling gear mechanism 62. Similar gear teeth 152 c are linearlydisposed on the opposite lateral side of bar 152 that faces smaller gear70 a of the locking mechanism 38. Smaller gear 70 a is arranged on ringmember 22 at a different higher plane than smaller gear 68 a, as seen inFIGS. 16 and 17. A switch 156 having a knob 158 is rotatably supportedby housing 146, switch 156 having a threaded post 156 a threadedlyconnected to a threaded opening 152 d in bar 152. In FIGS. 13 and 16,the bar 152 and switch 156 are in the first position, and as seen inFIG. 16 gear teeth 154 b are in engagement with smaller gear 68 a. Inthis first position, gear teeth 152 c do not engage smaller gear 70 a.Rotation of switch 156 by knob 158 to the position illustrated in FIG.15 rotates threaded post 156 a causing bar 152 to elevate in a lineardirection generally orthogonal to axis 152 a to the second position. Asseen in FIG. 17, in this second position gear teeth 152 c are inengagement with smaller gear 70 a while gear teeth 152 b do not engagesmaller gear 68 a. In all other respects, the retractor with thealternative arm arrangement functions in the same manner as set forthregarding the embodiments previously described hereinabove.

It should also be appreciated that while the particular arrangement ofretractor 10 has been described herein as a four bladed retractor,retractor 10 may be configured for use with as few as two blades or morethan four. It should further be appreciated that while it is desirablein some instances for all of the blades to be independentlytranslatable, there may be certain situations wherein a pair of blades12, such as those in quadrants A and B are jointly engageable with maingear 32 through clutch mechanism 36 by movement of a single switch 56.In addition, there may be certain other applications wherein one or moreblades of the retractor are fixed relative to frame 14 with at least onearm 28 and the blade supported thereon being selectively engageable withmain gear 32 through clutch mechanism 36.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same should be considered asillustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been presented and that all changes,modifications and further applications that come within the spirit ofthe invention are desired to be protected. Also, while the illustratedembodiments have been directed particularly to a retractor for use inspinal surgery, it should be understood that variations may be made tothe retractor to enable use in the expansion of bodily tissue in othersurgical procedures. Modifications in size may be necessary dependingupon the bodily tissue to be retracted.

What is claimed is:
 1. A kit of parts adapted for use in retracting bodytissue, comprising: a retractor, comprising a frame defining a generallycentral interior space, a plurality of arms for radial translationalmovement on said frame, a generally circular main gear rotatablysupported on said frame, an actuator gear supported by said frame forrotating said main gear, and a gear mechanism on each said arm forselective engagement and disengagement with said main gear forselectively translating said arms; and a plurality of retractor membersadapted to be selectively attached to said arms thereon for radialtranslational movement on said frame, a portion of each said retractormember adapted to extend into said interior space.
 2. The kit of partsof claim 1, wherein said retractor members include sets of blades ofdiffering lengths, said retractor members being adapted to beselectively attached to said arms such that said blades projectsubstantially transversely downwardly from said frame into said interiorspace.
 3. The kit of parts of claim 2, wherein the length of bladesranges from 9 cm to 17 cm.
 4. The kit of parts of claim 2, wherein eachblade includes an outer convex surface.
 5. The kit of parts of claim 2,wherein said plurality of arms comprises four arms.
 6. The kit of partsof claim 2, further including a mounting bracket adapted to attach tosaid frame at no less than two mounting positions on said frame, saidmounting bracket including a portion adapted to connect a mounting armto an operating table.
 7. The kit of parts of claim 1, further includinga tool with a T-handle adapted to actuate said actuator gear.
 8. The kitof parts of claim 1, further including illumination elements adapted tobe used in conjunction with one or more retractor members.
 9. A kit ofparts adapted for use in retracting body tissue, comprising: a retractorcomprising a frame defining a generally central interior space andplural mounting positions which are adapted to connect said frame to anoperating table, at least one arm including a retractor member thereonsupported for radial translational movement on said frame, a portion ofsaid retractor member extending into said interior space; and a mountingbracket adapted to attach to said frame at no less than two mountingpositions on said frame, said mounting bracket including a portionadapted to connect a mounting arm to an operating table.
 10. The kit ofparts of claim 9, further comprising a mounting arm adapted forconnecting to said portion of said mounting bracket and said operatingtable.
 11. The kit of parts of claim 9, wherein said retractor comprisesa plurality of arms, each arm being supported on said frame forselective radial translational movement on said frame, each armincluding a retractor member.
 12. The kit of parts of claim 11, whereineach of said retractor members is adapted to be selectively attached toa respective arm and wherein said kit includes a plurality of saidretractor members.
 13. The kit of parts of claim 12, wherein each ofsaid retractor member comprises a blade and wherein said kit includesretractor members having blades of differing lengths.